Materials and Methods Subjects Fifteen hearing aid users with prelingual severe to profound hearing loss participated in this study. Another six hearing aid users with a similar age and hearing average were included as the control group. The inclusion criteria for the study subjects and controls were: (1) age above 15 years; (2) wearing a hearing aid for at least for 2 years after hearing loss was diagnosed; (3) basic ability to operate a computer; (4) Mandarin Chinese speaker; and (5) motivation to undertake the training program. The exclusion criteria were: (1) aided hearing average worse than 70 dBHL; (2) unable to operate a computer. Before training with CAST, all participants received unaided and aided sound field audiometry. Table 1 shows the basic information of the 21 participants.